The disclosure relates to systems and methods for optically measuring creep and, more specifically, measuring creep of rotating components.
Gas turbines typically include a compressor section, a combustion section, and a turbine section. The compressor section pressurizes air flowing into the turbine. The combustion section receives the pressurized air, mixes it with fuel, and combusts the mixture. The turbine section receives the combustion flow from the combustion section to drive the turbine and generate power. Various components along the flow path, particularly in the compressor and turbine sections, rotate around one or more central axis during operation. These rotating components are subject to wear, swell, shrink, and migration during use. Rotating components are subject to creep due to the high temperatures and stresses during operation and may be permanently deformed. Significant deformation can lead to loss of efficiency and mechanical failure in some systems. Rotating components may be periodically or occasionally inspected to assure continued operation and/or schedule maintenance or end of service.
Conventional methods of measuring gas turbine components for creep have required system tear down and removal of such components in order to precisely measure strain within the component. For high availability systems, this can be problematic and create a significant loss in productivity.
Visual and, more specifically, digital image based measurement methods have been employed for measuring creep in some components, though often with the requirement of a precision fixture to enable image correlation that requires removal of the component from the gas turbine. Removal of rotating components may be particularly undesirable. Image-based analysis of a coupon or pattern attached to a component for strain information may also require a field of view sufficient to capture the entire coupon or pattern. In situ rotating components may be difficult to capture in a single image.